24 Aug
2012
24 Aug
'12
11:44 a.m.
Liam Proven wrote:
Hey, John, welcome! Have you just joined or been here
lurking all along?
Just joined.
In CP/M, isn't the BIOS just a file on disk
anyway?
It is, but adding functionality to it without the loadable driver
facility would be nowhere near as straightforward. You'd need to work
out how to allocate memory to your additional feature, how to hook it
into the various BIOS data structures, and then how to get the .EMS
self-unpacker to relocate it to the right place. And since it would be
infringement of copyright to distribute the patched file, you'd have to
distribute a program that did that patching.
Chuck Guzis wrote:
Suppose I wanted to use 1.44M 3.5" floppies. The
hardware (with a
bit of tweaking) is capable of it. No way to get to the boot
software, however. Suppose I wanted to boot from a home-built CF
card...
In theory you could replace the boot ROM (desolder the 8041, read its
contents, and burn an 8741 with the new boot image. Or even an 8742, if
you wanted more than 256 bytes of boot program). In the 9512 it would be
even easier, because the corresponding microcontroller used an external ROM.
It was also possible for peripherals plugged into the expansion port to
provide their own boot ROMs; Cirtech's external hard drives did so, for
example, and they advertised a similar device that booted from flash.
--
John Elliott